Tires traction ability is limited. If, before entering a corner, the tires' traction is used to 100% for braking, a steering input to change the direction will cause understeer. In trail braking the driver decreases the braking to leave some traction potential for steering. The challenge is to balance the braking and steering at the limit of tires traction and one of the ways to practice the skill is to imagine a string attached between the bottom of the steering wheel and left foot[1]. When the steering wheel is straight, the foot can be all the way down braking. When turning a wheel the driver decreases the braking force.